Abstract
Intracisternal injection of bethanidine in rats decreased brain norepinephrine [NE] turnover without affecting its endogenous level, and increased both cardiac NE turnover and serum corticosterone [B] level. A negative correlation was observed between brain NE turnover rate and serum B level. When cardiac NE turnover was suppressed by i.p. injection of bethanidine, serum B did not change significantly. Next, ether inhalation was added after intracisternal injection of bethanidine. Then, serum B increased more even when brain NE turnover was suppressed only slightly. Serum B may increase by selective decrease in brain NE turnover via the humoral route, from the hypothalamus down to the adrenal cortex. Inversely, intracisternal injection of B increased brain NE turnover. Brain NE may play an inhibitory role in the tonic regulation of CRF[corticotropin releasing factor]-ACTH secretion in the higher center than the hypothalamus and there may be closed-loop feedback system between brain NE and serum B.